Castiglione, writing in the 16th century is noted as a renaissance writer, and his role was that of giving advice to the young men of the aristocracy. However, do not expect much similarity to the gems of essential wily wisdom offered by that other 16th century statesman and political scientist, Machiavelli, and do not expect pointed, shrewd and perceptive psychological insights of a similar quality to those that La Rochefoucauld offered the elite aristocrats in the 17th century.
Castiglione however, I found to be interesting for anthropological or sociological reasons. We gain insight into the roles of women, and the assumption that men were innately superior beings - Castiglione teaches that women are inferior, somewhat wretched beings, aspiring for cosmic and heavenly perfection when they form bonds with men - whilst men are corrupted and made imperfect by their bonds with women.
We also learn about men's tastes in art, and fashion - Castiglione chastises a fashion amongst the idle rich of wearing eye liner and plucking their eye brows, and behaving in an effeminate manner, whilst he advises his charge to be manly, taking care of his physical form, that should be as masculine as imposing as possible, yet, graceful and dignified. The young aristocrat should also ensure that he studies painting and classical Greek and Roman literature.
Of interest too, is Castiglione's teachings regarding how the aristocracy should hold on to their power and encourage faithfulness from his peasant class, and in these verses, we also gain insight into what newly emerging concepts of `nation', `patriotism' and `identity' meant in the 16th century - one might speculate that these national identities meant far more to the aristocrats, who had much to gain from such definitions and sense of belonging, whilst to the peasant, these notions probably meant little more than fulfilling the roles of a diligent servant and as cannon fodder in times of war and strife.
Castiglione also gives advice on a number of other topics, such as how to behave in company of ones equals, superiors and inferiors - Castiglione advises respect for the concepts of otherworldliness and detachment displayed by the philosopher and religious figures -- but the young aristocrat should realise these are not at all the correct ways for a worldly man to behave, should he wish to gain respect from fellow aristocrats, statesmen and his servants, the peasant and common man.
Castiglione's book is interesting, but as mentioned before -- do not expect the insights of others 16th century writers such as Machiavelli, whose wisdom we can still apply today to an understanding of realist schools of thought, political science and international relations.